Biomedical subjects

Takafumi Maeda

Publications and source records attributed to Takafumi Maeda.

11 recordsLinked to original sources

PubMed2006

Risk factors for heatstroke among Japanese forestry workers.

We examined the risk factors for heatstroke among forestry workers in Japan during the summer. We distributed a questionnaire to 124 forestry workers to determine heatstroke symptoms, degree of sweating and hydration, as well as perceived hotness and amount of sunlight at work sites. Forty of the workers (32.3%) reported experiencing heatstroke symptoms. Thirteen and 21 of them reported such symptoms during July and August, respectively. Eleven workers experienced heatstroke at around 14:00; 5 and 4 developed symptoms at around 11:00 and 10:00, respectively. Groups with and without heatstroke symptoms significantly differed in terms of perceived hotness (p<0.05), sunlight (p<0.05), degree of sweating (p<0.01) and frequency of hydration (p<0.05) while working. Heatstroke symptoms developed in 60.6% of workers aged up to 50 yr, but in only 22.0% of those over the age of 51 (p<0.01). Multiple regression analysis selected the following key variables associated with the development of heatstroke symptoms (R(2)=0.236 and p=0.006): frequency of urination, hotness, BMI and years of forestry work (standard coefficients: +0.229, +0.194, +0.280 and -0.162, respectively). The results of the present study showed that one third of forestry workers developed some symptoms of early heatstroke during summer forestry work. Furthermore, the results indicate that a short duration of forestry service was one of the risk factors contributing to the onset of heatstroke, in addition to heat stress, loss of body water and electrolytes, and obesity.

Aged↗

PubMed2006

Physiological anthropology design: a comparative study between Germany and Japan.

With the recent globalization of industrial products, there is doubt as to whether the methodology of Physiological Anthropology has also been standardized. The purpose of this study is to assess signs of standardization through a comparative analysis of Physiological Anthropology design in Germany and Japan. This survey investigates its characteristics through four factors: comfort, usability, sensation and aesthetics. Both nations regard the first three indicators as important. The difference in assessment is, however, considerable. While German physiological anthropologists use subjective evaluation by means of questionnaires, somatometry and biomechanical analysis, their Japanese counterparts apply physiological measurements of the higher nervous system and the autonomic nervous system. Polymorphism and improving functional potentiality have recently gained increasing respect in Japan. Notions of aesthetics are not consciously analyzed in both countries. If the sense of beauty of product design relates to a physical and mental response, developing a systematic analysis on this factor would be a useful task for Physiological Anthropology.

Anthropology, Physical↗

PubMed2005

Perspectives on environmental adaptability and physiological polymorphism in thermoregulation.

The environmental adaptability of human beings has progressed according to various environments experienced in the course of evolution. Therefore, various phenotypes for environmental adaptability exist and are considered to be physiological polymorphism. Physiological polymorphism in thermoregulation is influenced by genotype, individual characteristics, environmental factors, cultural factors, etc. Moreover, it is thought that physiological polymorphism is evidenced more clearly in physiological responses to extreme situations and/or changing conditions than in environments where homeostasis is easily maintained. In the field of physiological anthropology, I think that it is important not only to discover the physiological responses that demonstrate polymorphism, but also to hypothesize about the mechanisms and the processes by which such polymorphisms were formed, and their meaning for human beings. Such discussions may be supposed to lead to an evaluation of the environmental adaptability of humans from the viewpoint of physiological anthropology.

Acclimatization↗

PubMed2005

Error and individual difference in cardiovascular responses to orthostatic stress in humans.

Variations in cardiovascular responses to orthostatic stress were investigated in terms of physiological polymorphism. Variations of physiological measurements are subdivided into individual differences and measurement errors. However, individual differences are often considered to be an error in statistical analysis due to its limitations in experimental design. In order to discuss about the relative contribution of individual difference in cardiovascular responses to postural changes, percent contribution (PC) was estimated using the Taguchi method. Six healthy male adults (age range: 21-27) were subjected to orthostatic stress by inducing a postural inclination of 60 degrees head-up-tilting to the horizontal, and the responses were measured thrice in each subject on different days. The respective changes of heart rate (HR) and stroke volume (SV) in the period from the resting supine to the head-up-tilt position were significantly increased (p < 0.01) and decreased (p < 0.01) without affecting the mean blood pressure (MBP). The PC of individual difference in HR showed a significantly higher ratio of individual difference during the head-up-tilt (71.4-76.2%) compared with supine rest (0.0-50.4%). While the main variations of HR during supine rest were not the individual differences between the subjects, the day-to-day differences within the subject were significant. The PC of individual differences in MBP and SV constantly displayed a significant difference between the subjects. These results suggest that the strategy for maintaining stable cardiovascular regulation may be different even in normal subjects. In the perspective of physiological parameters, PC monitoring may serve as an empirical approach to evaluate physiological polymorphism.

Adult↗

PubMed2005

Relationship between individual difference in melatonin suppression by light and habitual bedtime.

The purpose of this study was to determine the relationship between individual difference in melatonin suppression by exposure to light and habitual bedtime. Seventeen healthy male students (mean age: 22.6+/-2.4 yr) volunteered to participate in the study. The subjects were exposed to light (1000 lx) for 2 hours from 2 hours before the time of peak salivary melatonin concentration. Two hours after exposure to the light, melatonin suppression had occurred in fifteen subjects. No significant correlation was found between the rate of melatonin suppression and habitual bedtime in the fifteen subjects in whom melatonin suppression occurred. However, the habitual bedtime of the two subjects in whom melatonin suppression did not occur was earlier than that of the other subjects. These results suggest that there are some people with very low sensitivity to light and that this may affect habitual bedtime.

Adult↗

PubMed2005

Effects of lifestyle, body composition, and physical fitness on cold tolerance in humans.

In the present study, we attempted to clarify the effects of lifestyle and body compositions on basal metabolism and to clarify the effects of physical training on thermoregulatory responses to cold. Basal metabolism, body compositions, and questionnaires regarding lifestyle were evaluated in 37 students. From multiple linear regression analysis, sex, muscle weight, fat intake, and diurnal temperature were selected as significant explanatory variables. In a second experiment, rectal and the skin temperature at 7 different points as well as the oxygen uptake of eight males were measured at 10 degrees C for 90 min before and after training. The decline in rectal temperature that was observed before training was not observed after training. In addition, rectal temperature was significantly higher at post-training than at pre-training. These results suggest that some lifestyle factors affect cold tolerance; in particular, daily activity might improve our ability to control heat radiation and basal heat production.

Adaptation, Physiological↗

PubMed2004

Greater frequency of distraction accelerates bone formation in open-wedge proximal tibial osteotomy with hemicallotasis.

BACKGROUND: In chickens, increased distraction frequency stimulates bone formation in distraction osteogenesis. PATIENTS AND METHODS: We investigated the effect of two different distraction frequencies on bone formation in the distracted portion, and on the time of removal of the fixator, in open-wedge osteotomies of the proximal tibia with hemicallotasis (HCO). The study included 20 consecutive patients (20 knees) who underwent HCO for medial osteoarthrosis of the knee. 10 knees were distracted at a rate of 0.25 mm four times a day (the 4-step group); and the other 10 knees were distracted at a rate of 0.125 mm eight times a day (the 8-step group). RESULTS: There were no significant differences in the preoperative FTAs or the correction angles between the two groups. At all intervals until 6 weeks after the completion of distraction, bone mineral density in the distraction gap was significantly higher in the 8-step group than in the 4-step group. The average time in external fixation was 78 (SD 5) days in the 8-step group as compared to 89 (SD 6) days in the 4-step group, a significantly shorter time. INTERPRETATION: Our findings indicate that an increase in the distraction frequency in HCO provides better bone formation, resulting in a shorter external fixation period.

Aged↗

PubMed2004

Changes in health habits of female shift workers.

This paper examines the effects of shift work on the lifestyles of female factory workers. As an indicator of healthy lifestyle habits, we used a scoring system (referred to below as the 'health score') based on Lester Breslow's health habits. The 'health score' of the women was higher than that of the men, but the shift workers' score was lower than that of the non-shift workers (p<0.01). In addition, the score of workers who had changed from non-shift work to double-shift work was remarkably low (p<0.01). These results suggest that, while the female shift workers manage to maintain relatively healthy lifestyles in comparison with the males, they have more difficulty maintaining these habits than do female workers who do not perform shift work. It can be concluded that, in addition to heightening women's consciousness of their own health, surrounding entities such as the work environment, the home, and the community in general need to pay due care to Japan's female shift workers.

Adult↗

PubMed2004

[Effects of exposure to occupational hand-arm vibration on maintenance of postural balance].

In order to determine the relationship between exposure to hand-arm vibration through the use of vibration tools and dysfunction in the maintenance of postural balance, 106 male forestry workers were examined by stabilometry for deflection in the center of gravity and in the air conduction hearing levels. A questionnaire survey was also conducted among the workers in order to obtain details regarding their age, the types of tools used by them, and the duration for which they had used a chain saw. The vibration acceleration of a chain saw has been limited to a level of 3 G or less since 1976 in accordance with the notification from the Japanese Forestry Agency and the Ministry of Labor. In fact, chain saws with significantly reduced vibration acceleration in comparison with those used before 1976 have been available. Therefore, in 2000, we conducted a test on forestry workers who were divided into two groups-workers who had used a chain saw for 25 years or more (25-yr-or-more group) and workers who had used a chain saw for 24 yr or less (24-yr-or-less group). Compared to the 24-yr-or-less group, the 25-yr-or-more group exhibited significantly higher levels of average deflection in the center of gravity, expressed as the enveloped (aENV) and rectangular (aREC) areas, and in the hearing levels at 500, 1000, 2000, 4000 and 8000 Hz. For the aENV, the correlation coefficients revealed significant relationships between the hearing levels at 4,000 Hz, the duration of use of a chain saw, and age. Since the duration of use of a chain saw exhibited a significant relationship with age, it was necessary to eliminate the effect of age on the aENV. Subsequently, we divided all the workers into age groups spanning ten years each (from 20 to 70 yr) and compared the aENV among the same age groups in both the 25-yr-or-more and the 24-yr-or-less groups. The averages of the aENV for each age group were higher in the 25-yr-or-more group than in the 24-yr-or-less group. In particular, a significant difference was observed in the group of workers in their 40s. Moreover, the average of aENV value was significantly higher in the 25-yr-pr-more group than in the 24-yr-or-less group among the workers between 46 and 68 yr, with their ages being congruent in both groups. While investigating the impact on the workers who had used chain saws, it might be difficult to examine the effect of occupational vibration independent of the noise load. Nevertheless, this study suggests the possibility that a decrease in the maintenance of postural balance has a stronger relationship with exposure to thumping vibration in the past than with the age factor.

Adult↗

PubMed2004

Effect of shift work on mental state of factory workers.

This paper examines the effects of shift work on the mental state of factory workers. As an indicator of the workers' mental condition, the authors used a scoring system (referred to below as the 'depression tendency score') based on the SRQ-D investigative report. The depression tendency score of the men was higher among the shift worker group than among the regular day worker group (p < 0.01). The depression tendency score of the male back-to-back shift workers was higher than that of the male regular day workers among skilled workers (p < 0.05). Among the women, no notable difference in depression tendency score was observed between the regular day worker group and the shift worker group. However, the depression tendency score of the female two-shift workers was higher than that of the female regular day workers among skilled workers (p < 0.05). We conclude that the mental health of men is easily affected by back-to-back shift work and that of women is affected by two-shift work because of the difference in modern societal/home role between man and woman.

Adult↗

PubMed2003

A survey of urinary hippuric acid and subjective symptoms among occupational low toluene exposed workers.

Biological monitoring of toluene exposure by urinary hippuric acid determination and a subjective symptom survey by self-administered questionnaire were performed in 20 workers at low toluene exposure in factories to evaluate the health hazard including dysfunction of nervous system. Environmental monitoring was carried out using toluene gas detection tubes. Urine samples were collected three times a day in order to measure hippuric acid: first before the commencement of work, then at the end of forenoon work, and lastly at the end of afternoon work. Toluene vapor concentrations of throughout the workday ranged from 15.3 to 31.4 ppm. The urinary hippuric acid concentrations correlated with the toluene concentrations of ambient air (r = 0.58, p = 0.01). The subjective symptoms increased in close association with the exposure to toluene; the prevalence rate of subjective symptoms "during work" in the exposed group was 15 times higher than the rate of the non-exposed group (p < 0.0001). The prevalence rate of subjective symptoms "off-work" in the exposed group was 2.4 times higher than the rate of the non-exposed group (p < 0.0001), and also the prevalence rate of "nineteen symptoms off-work which are apparently related to central nervous system (CNS) and autonomic nervous system (ANS)" in the exposed group was 1.8 times higher than the rate of the non-exposed group (p < 0.05). From these results, these subjective symptoms, which have been believed to be complained in high organic solvent exposure should be reassessed and reconsidered in evaluating the nervous system dysfunction and local irritation in relatively low toluene exposed workers.

Adult↗